1. Field of the Invention
The present invention relates generally to earth boring bits of the type used to drill oil and gas wells and particularly to improvements in the bearing regions of rolling cutter bits achieved by applying titanium carbide modified hardfacing compositions to the friction bearing surfaces thereof.
2. Description of the Prior Art
As a bit bores through the earth, it experiences increasingly higher pressures and temperatures, while the abrasives that surround the bit create extremely destructive conditions. In order to improve bit life expectancy, continuing effort is directed toward improving the bearing surfaces of the rolling cutter bit.
At the present time, the bearing surfaces of rotatable cutters in earth boring drill bits are commonly carburized, hardened and tempered to increase their wear resistance. Gas carburizing is a known technique which has been used in the past to produce a uniform case on the head section bearings of earth boring drill bits. Pack carburizing is another technique used at the present time to treat the bearing areas of earth boring drill bits. A particulate carburizing compound is packed in a container which surrounds the drill bit bearing area which is to be treated. Other surface treatments of the bearing surfaces which have been used in the past include boronizing and combinations of carburizing and boronizing.
Although surface treatments of the above type have prolonged the useful life of rolling cutter rock bits, each method has associated disadvantages. For instance, the boronized "case" was typically very hard and thin. As a result, the boronized surfaces could not be ground after heat treatment to achieve dimensional accuracy. Carburized bearing surfaces tend to wear fairly quickly, although they can be ground after heat treatment.
Another prior art technique for improving the wear resistance of the bearing surfaces of rolling cutter rock bits was the application of "hard-metal alloy" hardfacing materials. In such processes, a hardfacing such as an iron-based alloy was supplied as a cast rod which was applied to the bearing surface by welding with an oxyactylene torch. These hardfacings allowed precision grinding to achieve dimensional accuracy but did not provide the improved wear resistance which was desired. Because of the disadvantages associated with surface treatment of the friction bearing surfaces, attention is again being directed to developing an improved hardfacing for the friction bearing surface of a rotary rock bit.
The present invention has as its object to provide such an improved hardfacing composition. Another object of the invention is to provide a method for manufacturing an earth boring bit having friction bearing surfaces with improved abrasion, adhesion and fatigue resistance using the hardfacing composition of the invention.